The invention relates to flexible disks in stacked relationship and more particularly to mechanism for moving an access arm carrying a magnetic transducer into the disk stack.
Previous such mechanisms have been used which utilize an electrical stepping motor for moving an access arm carrying a transducer longitudinally of a stack of flexible disks for positioning the access arm and transducer in desired positions along the length of the disk stack prior to moving the access arm and transducer radially into the stack. The stepping motor and the access arm of the transducer have been customarily moved a certain fixed number of steps for each of the flexible disks calculated to position the access arm longitudinally of the stack midway between the disks of each pair of disks throughout the stack. It has been found, however, that the flexible disks are not uniform and that some of them droop more than others, particularly under the action of gravity, assuming that the disk stack is vertical which is preferable. The disks also tend to flutter on their circumferences, and there also may be non-linearities in the positioning of the disks on their drive spindle. For these reasons, stepping the access arm and its transducer for a fixed, predetermined number of steps for each disk longitudinally of the stack in an attempt to position the access arm midway between consecutive pairs of disks throughout the stack is not an entirely satisfactory solution to the problem of positioning the access arm in position to read or write on particular disks in the stack.